Adding EGR for MPG

[aardvarcus]

I am contemplating adding EGR to a gasoline 4 stroke vehicle that presently has none. The engine is a 1999 Toyota 5vz fe 3.4L V6 in a 4Runner. Some installations of this engine had EGR, mine did not.

There are many reasons for EGR, my purpose of the EGR would be to reduce vacuum caused by the intake under partial throttle by adding air absent of oxygen post the MAF sensor. This should keep from messing with the air fuel ratio. The engine was designed for a supercharger so I assume the stock instrumentation should be sufficient to react to the addition of EGR without going out of range.

I dont believe the stock EGR system from other chassis would bolt on due to interferences, so this would be a custom EGR system. I was thinking cooled EGR collected further back in the exhaust post cats.

Thoughts?

[hayden55]

Originally Posted by aardvarcus

I am contemplating adding EGR to a gasoline 4 stroke vehicle that presently has none. The engine is a 1999 Toyota 5vz fe 3.4L V6 in a 4Runner. Some installations of this engine had EGR, mine did not.

There are many reasons for EGR, my purpose of the EGR would be to reduce vacuum caused by the intake under partial throttle by adding air absent of oxygen post the MAF sensor. This should keep from messing with the air fuel ratio. The engine was designed for a supercharger so I assume the stock instrumentation should be sufficient to react to the addition of EGR without going out of range.

I dont believe the stock EGR system from other chassis would bolt on due to interferences, so this would be a custom EGR system. I was thinking cooled EGR collected further back in the exhaust post cats.

Thoughts?

Why post cat? I thought the point was to recoup the lost energy and reburn it.

[aardvarcus]

There are different reasons for EGR, the typical reason usually being to reduce the temperature in the combustion chamber to prevent the forming of nox. My California emissions engine apparently did not require EGR for that purpose.

The purpose I would be wanting EGR for would be to simply fill the intake with inert gas (no oxygen) instead of having so much vacuum. It takes engine horsepower to create the vacuum. The assumption would be you would allow some exhaust gas to flow into the intake when the throttle is partially closed. I could do the same thing with a big nitrogen bottle, it would just need refilled. My assumption would be that cooled post cat exhaust gases would be the closest thing to a freely available gas without oxygen.

[slowmover]

The reason I went to an intake manifold where the EGR “jets” (RB Mopar) were mounted in the exhaust crossover (V8) was to help with my having advanced the timing curve against pre-ignition/detonation. Not really a solution. But being able to run premium gasoline with that curve WAS an increase in MPG.

[Ecky]

I considered adding EGR to my engine but after reading on it a bit, it appears Honda removed the EGR valve and lines because EGR effect could be accomplished with the VTC (variable cam timing) system. High advance at low load give a lot of valve overlap and a lot of exhaust gas doesn’t leave the cylinder.

[Daox]

I've wanted to do this with a few cars. Its just a bit of work to get it installed and working nicely.

I do think slapping on an EGR system will improve mileage. However, I think when you add tuning (ignition advance), you will see larger gains. There is also the issue of programming the EGR system itself.

All the newer engines are using cooled EGR so hot exhaust gases don't cause preignition when you use a lot of EGR. Otherwise, you get too much heat. This is the disadvantage to using VTC that Ecky mentioned. VTC doesn't allow the EGR to cool at all. However it is much simpler, and there is nothing to eventually clog up.